A tap changer for voltage regulation with semiconductor switching units is known from DE 10 2011 012 080 A1. The tap changer has two parallel load branches, and semiconductor switching units are connected in series in both load branches. In that case, a respective semiconductor switch of the first load branch and of the second load branch are mutually opposite in pairs. A respective sub-winding and bridge are connected, in alternation between these paired semiconductor switches, and switch between the two load branches. The sub-windings have different winding counts. The semiconductor switches can be constructed as thyristor pairs or IGBT pairs. The windings can be switched on and off by adept switching of the semiconductor switches. The step up or step down of the transformer can thereby be adapted and the voltage at the secondary side thus regulated. It is also possible, through use of IGBTs, to realize with the help of pulse-width modulation an alternating switching on and switching off of a sub-winding and to thereby implement a finely stepped voltage regulator. Switching losses arise due to constant switching-on and switching-off of the semiconductor switches and the semiconductor switches heat up, which imposes a high stress on the cooling device.